NEW YORK — Whitney Houston is back in rehab.

A representative for the superstar singer confirmed that Houston is undergoing treatment. Kristen Foster says Houston is in an out-patient program for drug and alcohol treatment. She says it is a voluntary measure and part of Houston’s “long-standing” recovery process.

It’s unclear how long Houston will be in rehab or where she’s being treated; Foster had no further comment. However, Houston has been visible recently: Last week, she sang on stage with Chaka Khan during Prince’s concert in Los Angeles.